Printing apparatus and printing method

ABSTRACT

There is provided a printing apparatus including: a driving roller which drives a recording medium in a predetermined direction by rotation thereof; a supporting member which supports the recording medium further on the downstream side in the predetermined direction than the driving roller; a discharge head which is provided to oppose the supporting member and discharges liquid to the recording medium supported by the supporting member; a tension control portion which adjusts tension of the recording medium supported by the supporting member by controlling tension of the recording medium based on a result of detecting tension of the recording medium further on the downstream side in the predetermined direction than the driving roller; and a first destaticizing portion which destaticizes the recording medium further on the upstream side in the predetermined direction than the driving roller.

BACKGROUND 1. Technical Field

The present invention relates to a technology for destaticizing arecording medium which is used in printing.

2. Related Art

A printing apparatus (printer) described in JP-A-2014-184665 includes arecording head disposed to oppose a rotation drum, and prints an imageon a recording medium by discharging ink from the recording head whilesupporting the recording medium (sheet) by the rotation drum. However,in the printing apparatus, there is a concern that various problemscaused by electrification of the recording medium occur.

As an example, there is a case where influence on a tension control ofthe recording medium is generated. In other words, in JP-A-2014-184665,a driving roller is provided further on an upstream side in a transportdirection of the recording medium than a supporting member (rotationdrum) which supports the recording medium. In addition, by controllingtension of the recording medium based on a result of detecting tensionof the recording medium further on the downstream side in the transportdirection than the driving roller, tension of the recording mediumsupported by the supporting member is controlled. According to this, itis possible to appropriately control tension of the recording medium onwhich liquid discharged from a discharge head lands. However, when therecording medium is electrified, the recording medium sticks to thedriving roller when passing through the driving roller. In addition,since the sticking of the recording medium to the driving rollerinfluences the detection result of tension of the recording medium,there is a case where the tension control of the recording medium is notappropriately performed (first problem).

Otherwise, as another example, there is a case where influence oncontamination of the discharge head is generated. In other words, whenthe recording medium is electrified, there is a tendency for mist-likeliquid to be likely to adhere to a front surface opposing to therecording medium of the discharge head. In addition, there is also asituation in which the adhesion of the mist-like liquid to the dischargehead cannot be easily eliminated by destaticization of the recordingmedium.

In other words, it is considered that a destaticizing device, such as anionizer, is used in destaticizing the recording medium. In addition, assuch a destaticizing device, a device which performs destaticizationusing ions generated by applying an AC voltage to a plurality ofarranged electrodes is known. However, since there is a tendency for alarge number of ions to be imparted being deviated to a part whichopposes the electrode in the recording medium, there is a case whereuneven destaticization caused by arrangement of the electrodes isgenerated and the mist-like liquid adheres to a location thatcorresponds to the uneven destaticization in the discharge head (secondproblem).

In addition, since an ion balance is not appropriate, there is a casewhere the recording medium supported by the supporting member cannot besufficiently destaticized and mist-like liquid adheres to the dischargehead which opposes the supporting member (third problem).

SUMMARY

The invention can be realized in the following aspects.

According to a first aspect of the invention, there is provided aprinting apparatus including: a driving roller which drives a recordingmedium in a predetermined direction by rotation thereof; a supportingmember which supports the recording medium further on the downstreamside in the predetermined direction than the driving roller; a dischargehead which is provided to oppose the supporting member and dischargesliquid to the recording medium supported by the supporting member; atension control portion which adjusts tension of the recording mediumsupported by the supporting member by controlling tension of therecording medium based on a result of detecting tension of the recordingmedium further on the downstream side in the predetermined directionthan the driving roller; and a first destaticizing portion whichdestaticizes the recording medium further on the upstream side in thepredetermined direction than the driving roller.

According to a second aspect of the invention, there is provided aprinting method including: driving a recording medium in a predetermineddirection by a driving roller by rotating the driving roller;destaticizing the recording medium by a destaticizing portion further onthe upstream side in the predetermined direction than the drivingroller; adjusting tension of the recording medium supported by thesupporting member by controlling tension of the recording medium basedon a result of detecting tension of the recording medium further on thedownstream side in the predetermined direction than the driving roller;and discharging liquid from a discharge head that opposes the supportingmember, to the recording medium supported by the supporting memberprovided further on the downstream side in the predetermined directionthan the driving roller.

In the invention (first and second aspects) configured in this manner,the recording medium is destaticized by the destaticizing portionfurther on the upstream side in the predetermined direction than thedriving roller which drives the recording medium in the predetermineddirection. Therefore, since the recording medium is destaticized whenpassing through the driving roller, sticking of the recording medium tothe driving roller is suppressed. As a result, it is possible toaccurately detect tension of the recording medium further on thedownstream side in the predetermined direction than the driving roller,and to appropriately perform the tension control of the recordingmedium.

In the printing apparatus, a discharger which performs surfacemodification treatment with respect to the recording medium by impartingdischarge energy to the recording medium further on the upstream side inthe predetermined direction than the first destaticizing portion, may beprovided. In other words, in the printing apparatus provided with thedischarger, since there is a tendency for an electrification amount ofthe recording medium to increase, influence on the tension controlincreases as the electrified recording medium sticks to the drivingroller. Meanwhile, it is possible to appropriately perform the tensioncontrol of the recording medium by destaticizing the recording medium bythe destaticizing portion further on the upstream side in thepredetermined direction than the driving roller.

In the printing apparatus, a second destaticizing portion whichdestaticizes the recording medium between the driving roller and thedischarge head, may be provided. In this manner, by destaticizing therecording medium in two steps until reaching the discharge head, it ispossible to definitely destaticize the recording medium, and toefficiently suppress adhesion of mist-like liquid to the discharge headdue to electrification of the recording medium.

In the printing apparatus, the second destaticizing portion may beprovided to oppose the supporting member. According to this, it ispossible to destaticize the recording medium in the vicinity of thedischarge head, and to suppress adhesion of mist-like liquid to thedischarge head due to the destaticization of the recording medium.

In the printing apparatus, a front surface of the supporting member maybe covered with an insulating layer. In other words, in a case where thefront surface of the supporting member has conductivity, there is aconcern that the ions generated by the destaticizing portion areoriented toward a part which is not hidden in the recording medium inthe supporting member, and the ions cannot be definitely imparted to therecording medium. Meanwhile, by covering the front surface of thesupporting member with the insulating layer, it is possible todefinitely impart the ions generated by the destaticizing portion to therecording medium, and to reliably destaticize the recording medium.

In the printing apparatus, the first destaticizing portion and thesecond destaticizing portion may destaticize the recording medium byimparting ions generated by applying an AC voltage to a plurality ofarranged electrodes to the recording medium, and an amplitude of an ACvoltage generated in the recording medium by the AC voltage applied tothe electrode of the second destaticizing portion may be smaller than anamplitude of an AC voltage generated in the recording medium by the ACvoltage applied to the electrode of the first destaticizing portion.

In the configuration, the first destaticizing portion disposed on theupstream side and the second destaticizing portion disposed on thedownstream side are provided in the predetermined direction in which therecording medium is transported. In addition, an AC voltage having arelatively large amplitude is generated in the recording medium by theAC voltage applied to the electrode of the first destaticizing portion.Therefore, a large difference in applying amount of ions between a partat which the ions are tightly imparted and a part at which the ions aresparsely imparted is generated, and uneven destaticization is likely tobe generated in the recording medium destaticized by the firstdestaticizing portion. Meanwhile, the second destaticizing portionfurther destaticizes the recording medium after the destaticization bythe first destaticizing portion. Moreover, the amplitude of the ACvoltage generated in the recording medium by the AC voltage applied tothe electrode of the second destaticizing portion is relatively small.Therefore, the second destaticizing portion can similarly destaticizethe recording medium compared to the first destaticizing portion, and itis possible to mitigate uneven destaticization of the recording mediumafter the destaticization by the first destaticizing portion. As aresult, it is possible to suppress adhesion of mist-like liquid to thedischarge head.

In the printing apparatus, the first destaticizing portion may have aplurality of electrodes provided on one surface side of the recordingmedium and a plurality of electrodes provided on the other surface sideof the recording medium, and a phase of the AC voltage applied to theplurality of electrodes on the one surface side and a phase of the ACvoltage applied to the plurality of electrodes on the other surface sidemay be different from each other by 180 degrees. Otherwise, in theprinting apparatus, an interval between the electrode of the firstdestaticizing portion and the recording medium may be narrower than aninterval between the electrode of the second destaticizing portion andthe recording medium. In the printing apparatuses, an AC voltage havinga relatively large amplitude is generated in the recording medium by theAC voltage applied to the electrode of the first destaticizing portion.Here, it is appropriate to mitigate uneven destaticization of therecording medium after the destaticization by the first destaticizingportion by providing the second destaticizing portion as describedabove.

In the printing apparatus, a pitch at which the plurality of electrodesare arranged in the first destaticizing portion may be different from apitch at which the plurality of electrodes are arranged in the seconddestaticizing portion. In this manner, by making the pitches at whichthe electrodes are arranged different in the first destaticizing portionand in the second destaticizing portion, it is possible to moreefficiently mitigate uneven destaticization of the recording mediumafter the destaticization by the first destaticizing portion by usingthe second destaticizing portion.

In the printing apparatus, an adjustment portion which adjusts an ionbalance of the first destaticizing portion; and a potential detectorwhich detects a potential of the recording medium supported by thesupporting member, may be provided. In the configuration, it is possibleto adjust an ion balance of the destaticizing portion while confirmingthe detection result of the potential of the recording medium supportedby the supporting member. Therefore, it is possible to optimize the ionbalance. As a result, it is possible to suppress adhesion of mist-likeliquid to the discharge head.

In the printing apparatus, a balance control portion which controls anion balance of the first destaticizing portion by adjusting the ionbalance of the first destaticizing portion may be provided in theadjustment portion based on the detection result of the potentialdetector. In the configuration, it is possible to automatically optimizethe ion balance by the balance control portion.

In the printing apparatus, a display portion which displays thedetection result of the potential detector; and a balance controlportion which adjusts an ion balance of the first destaticizing portionin the adjustment portion in accordance with an input operation, may beprovided. In the configuration, it is possible to optimize the ionbalance by performing an input operation while confirming the detectionresult of the potential detector displayed on the display portion by auser.

According to a third aspect of the invention, there is provided aprinting apparatus including: a transport portion which transports arecording medium in a predetermined direction; a supporting member whichsupports the recording medium; a discharge head which is provided tooppose the supporting member and discharges liquid to the recordingmedium supported by the supporting member; a first destaticizing portionwhich is provided further on the upstream side in the predetermineddirection than the discharge head, and destaticizes the recording mediumby imparting ions generated by applying an AC voltage to a plurality ofarranged electrodes to the recording medium; and a second destaticizingportion which is provided between the first destaticizing portion andthe discharge head, and destaticizes the recording medium by impartingions generated by applying an AC voltage to a plurality of arrangedelectrodes to the recording medium, in which an amplitude of an ACvoltage generated in the recording medium by the AC voltage applied tothe electrode of the second destaticizing portion is smaller than anamplitude of an AC voltage generated in the recording medium by the ACvoltage applied to the electrode of the first destaticizing portion.

According to a fourth aspect of the invention, there is provided aprinting method including: transporting a recording medium in apredetermined direction; discharging liquid to the recording mediumsupported by a supporting member from a discharge head provided tooppose the supporting member; destaticizing the recording medium byimparting ions generated by applying an AC voltage to a plurality ofarranged electrodes in a first destaticizing portion provided further onthe upstream side in the predetermined direction than the dischargehead, to the recording medium; and destaticizing the recording medium byimparting ions generated by applying an AC voltage to a plurality ofarranged electrodes in a second destaticizing portion provided betweenthe first destaticizing portion and the discharge head, to the recordingmedium, in which an amplitude of an AC voltage generated in therecording medium by the AC voltage applied to the electrode of thesecond destaticizing portion is smaller than an amplitude of an ACvoltage generated in the recording medium by the AC voltage applied tothe electrode of the first destaticizing portion.

In the invention (third and fourth aspects) configured in this manner,the first destaticizing portion disposed on the upstream side and thesecond destaticizing portion disposed on the downstream side areprovided in the predetermined direction in which the recording medium istransported. In addition, an AC voltage having a relatively largeamplitude is generated in the recording medium by the AC voltage appliedto the electrode of the first destaticizing portion. Therefore, a largedifference in applying amount of ions between a part at which the ionsare tightly imparted and a part at which the ions are sparsely impartedis generated, and uneven destaticization is likely to be generated inthe recording medium destaticized by the first destaticizing portion.Meanwhile, the second destaticizing portion further destaticizes therecording medium after the destaticization by the first destaticizingportion. However, the amplitude of the AC voltage generated in therecording medium by the AC voltage applied to the electrode of thesecond destaticizing portion is relatively small. Therefore, the seconddestaticizing portion can similarly destaticize the recording mediumcompared to the first destaticizing portion, and it is possible tomitigate uneven destaticization of the recording medium after thedestaticization by the first destaticizing portion. As a result, it ispossible to suppress adhesion of mist-like liquid to the discharge head.

According to a fifth aspect of the invention, there is provided aprinting apparatus including: a transport portion which transports arecording medium in a predetermined direction; a supporting member whichsupports the recording medium; a discharge head which is provided tooppose the supporting member and discharges liquid to the recordingmedium supported by the supporting member; a destaticizing portion whichis provided further on the upstream side in the predetermined directionthan the discharge head, and destaticizes the recording medium byimparting ions generated by applying an AC voltage to arrangedelectrodes to the recording medium; an adjustment portion which adjustsan ion balance of the destaticizing portion; and a potential detectorwhich detects a potential of the recording medium supported by thesupporting member.

According to a sixth aspect of the invention, there is provided aprinting method including: transporting a recording medium in apredetermined direction; discharging liquid to the recording mediumsupported by a supporting member from a discharge head provided toopposes the supporting member; destaticizing the recording medium byimparting ions generated by applying an AC voltage to arrangedelectrodes in a destaticizing portion provided further on the upstreamside in the predetermined direction than the discharge head, to therecording medium; detecting a potential of the recording mediumsupported by the supporting member; and adjusting an ion balance of thedestaticizing portion based on the detected potential.

In the invention (fifth and sixth aspects) configured in this manner, itis possible to adjust the ion balance of the destaticizing portion whileconfirming the detection result of the potential of the recording mediumsupported by the supporting member. Therefore, it is possible tooptimize the ion balance. As a result, it is possible to suppressadhesion of mist-like liquid to the discharge head.

In addition, in order to solve a part or the entirety of theabove-described problem, or in order to achieve a part or the entiretyof the effects described in the specification, all of theabove-described plurality of configuration elements in each aspect ofthe invention are not necessary, and a part of the plurality ofconfiguration elements can be appropriately changed, removed, orswitched to other new configuration elements, and partial removal oflimited contents is possible. In addition, in order to solve a part orthe entirety of the above-described problem, or in order to achieve apart or the entirety of the effects described in the specification, apart or the entirety of technical characteristics included in one aspectof the above-described invention can be combined with a part or theentirety of the technical characteristics included in otherabove-described aspects of the invention, and can also be oneindependent aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a view illustrating an inner configuration of a printer whichemploys the invention.

FIG. 2 is a view illustrating a configuration of a first destaticizingportion.

FIG. 3 is a view illustrating a configuration of a second destaticizingportion.

FIG. 4 is a view illustrating an electric configuration which controlsthe printer.

FIG. 5 is a view illustrating a configuration in which a first controlexample of destaticizing processing of a sheet is performed.

FIG. 6 is a view illustrating a temporal change in voltage generated bythe first and second destaticizing portions on the sheet.

FIG. 7 is a view illustrating a configuration in which a second controlexample of the destaticizing processing of the sheet is performed.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 a front view schematically illustrating an example of an innerconfiguration of a printer which employs the invention. As illustratedin FIG. 1, in a printer 1, one sheet S (web) of which both ends arewound around a delivery shaft 20 and a winding shaft 40 in a rolledshape stretches between the delivery shaft 20 and the winding shaft 40,and the sheet S is transported to the winding shaft 40 from the deliveryshaft 20 along a transport path Pc which stretches in this manner. Inother words, each of both ends of the sheet S is wound in a rolledshape, a delivery roll R20 and a winding roll R40 are formed, and thesheet S is transported in a roll-to-roll manner along a transportdirection Ds toward the winding roll R40 that is pivotally supported bythe winding shaft 40 from the delivery roll R20 which is pivotallysupported by the delivery shaft 20.

In addition, in the printer 1, an image is recorded on the sheet Stransported in the transport direction Ds. The type of the sheet S isbroadly classified into a paper type and a film type. Specific examplesof the paper type include a pure paper sheet, a cast paper sheet, an artpaper sheet, or a coated paper sheet, and specific examples of the filmtype include a synthetic paper sheet, a polyethylene terephthalate (PET)or a polypropylene (PP). Schematically, the printer 1 includes adelivery portion 2 (delivery region) which delivers the sheet S from thedelivery shaft 20, a process portion 3 (process region) which records animage on the sheet S delivered from the delivery portion 2, and awinding portion 4 (winding region) which winds the sheet S on which theimage is recorded by the process portion 3 around the winding shaft 40.In addition, in the following description, regarding two surfaces of thesheet S, while a surface on a side that opposes a recording head 51 isreferred to as a front surface, a surface on a side reverse thereto isreferred to as a rear surface.

The delivery portion 2 includes the delivery shaft 20 around which anend of the sheet S is wound, and a driven roller 21 around which thesheet S pulled out from the delivery shaft 20 is wound. The deliveryshaft 20 winds and supports the end of the sheet S in a state where thefront surface of the sheet S is toward the outside. In addition, as thedelivery shaft 20 rotates in a clockwise direction of FIG. 1, the sheetS wound around the delivery shaft 20 is delivered to the process portion3 via the driven roller 21. Incidentally, the sheet S is wound aroundthe delivery shaft 20 via a core tube 22 which is attachable to anddetachable from the delivery shaft 20. Therefore, when the sheet S ofthe delivery shaft 20 is used up, a new core tube 22 around which therolled sheet S is wound is mounted on the delivery shaft 20, and thesheet S of the delivery shaft 20 can be exchanged.

In addition, in the delivery portion 2, a corona treatment device 7 isdisposed between the delivery shaft 20 and the driven roller 21 in thetransport direction Ds of the sheet S. The corona treatment device 7includes a supporting roller 71 around which the sheet S that reachesthe driven roller 21 from the delivery shaft 20 is wound from a rearsurface side, and a corona discharger 73 which opposes the front surfaceof the supporting roller 71 via the sheet S. The supporting roller 71 isgrounded and functions as an earth electrode. Meanwhile, the coronadischarger 73 includes a corona discharge electrode 731, and anelectrode cover 733 which covers the corona discharge electrode 731. Thecorona discharge electrode 731 is disposed to oppose the supportingroller 71 via the sheet S, and causes corona discharge between thesupporting roller 71 and the corona discharge electrode 731 whenreceiving voltage application. In this manner, by imparting energy ofcorona discharge to the front surface of the sheet S wound around thesupporting roller 71, the corona treatment (surface modificationtreatment) is performed with respect to the front surface of the sheetS.

Furthermore, the delivery portion 2 includes a first destaticizingportion 81 provided further on the downstream side in the transportdirection Ds than the driven roller 21. The first destaticizing portion81 includes a front surface ionizer 82 which opposes the front surfaceof the sheet S, and a rear surface ionizer 83 which opposes the rearsurface of the sheet S, and destaticizes the sheet S by the ionizers 82and 83. In this manner, the delivery portion 2 delivers the sheet Sdestaticized by the first destaticizing portion 81 to the processportion 3 after receiving the surface modification treatment by thecorona treatment device 7.

The process portion 3 records an image on the sheet S by appropriatelyperforming the treatment by each of the functional portions 51, 52, 61,62, and 63 which are disposed along the outer circumferential surface ofa rotation drum 30 while supporting the sheet S delivered from thedelivery portion 2 by the rotation drum 30. In the process portion 3, ainfeed roller 31 and a outfeed roller 32 are provided on both sides ofthe rotation drum 30, the sheet S transported to the outfeed roller 32from the infeed roller 31 is supported by the rotation drum 30 andreceives the image recording.

The infeed roller 31 has a plurality of fine projections formed bythermal spraying on an outer circumferential surface, and supports thesheet S delivered from the delivery portion 2 from the rear surfaceside. In addition, the infeed roller 31 transports the sheet S deliveredfrom the delivery portion 2 to the downstream side in the transportdirection Ds by rotation thereof in a clockwise direction of FIG. 1. Inaddition, a nip roller 31 n is provided with respect to the infeedroller 31. The nip roller 31 n abuts against the front surface of thesheet S in a state of being biased to the infeed roller 31 side, andnips the sheet S between the nip roller 31 n and the infeed roller 31.According to this, a friction force is ensured between the infeed roller31 and the sheet S, and it is possible to reliably transport the sheet Sby the infeed roller 31.

The rotation drum 30 is, for example, a cylindrical drum which issupported to be rotatable by a supporting mechanism that is notillustrated, and has a diameter of 400 [mm], and the sheet S transportedto the outfeed roller 32 from the infeed roller 31 is wound from therear surface side. The rotation drum 30 supports the sheet S from therear surface side while rotating to be driven in the transport directionDs of the sheet S by receiving the friction force between the rotationdrum 30 and the sheet S. In other words, in the process portion 3,driven rollers 33 and 34 which fold back the sheet S on both sides of awinding portion to the rotation drum 30 are provided. The driven roller33 of the driven rollers folds back the sheet S by winding the frontsurface of the sheet S between the infeed roller 31 and the rotationdrum 30. Meanwhile, the driven roller 34 folds back the sheet S bywinding the front surface of the sheet S between the rotation drum 30and the outfeed roller 32. In this manner, by folding back the sheet Son each of the upstream side and the downstream side in the transportdirection Ds with respect to the rotation drum 30, it is possible toensure the winding portion of the sheet S to the rotation drum 30 to belong.

The outfeed roller 32 includes a plurality of fine projections formed bythermal spraying on an outer circumferential surface, and supports thesheet S transported via the driven roller 34 from the rotation drum 30,from the rear surface side. In addition, the outfeed roller 32transports the sheet S to the winding portion 4 by rotation thereof in aclockwise direction of FIG. 1. In addition, a nip roller 32 n isprovided with respect to the outfeed roller 32. The nip roller 32 nabuts against the front surface of the sheet S in a state of beingbiased to the outfeed roller 32 side, and nips the sheet S between thenip roller 32 n and the outfeed roller 32. According to this, a frictionforce is ensured between the outfeed roller 32 and the sheet S, and itis possible to reliably transport the sheet S by the outfeed roller 32.

In this manner, the sheet S transported to the outfeed roller 32 fromthe infeed roller 31 is supported on the outer circumferential surfaceof the rotation drum 30. In addition, in the process portion 3, in orderto record a color image on the front surface of the sheet S supported bythe rotation drum 30, the plurality of recording heads 51 whichcorrespond to colors different from each other are provided.Specifically, four recording heads 51 which correspond to yellow, cyan,magenta, and black are aligned in the transport direction Ds in thiscolor order. Each of the recording heads 51 opposes the front surface ofthe sheet S wound around the rotation drum 30 at a slight clearance, anddischarges ink having a corresponding color (color ink) from a nozzle inan ink jet method. In addition, as each of the recording heads 51discharges the ink to the sheet S transported in the transport directionDs, a color image is formed on the front surface of the sheet S.

Incidentally, as ink, ultraviolet (UV) ink (photo-curing ink) which iscured by being irradiated with an ultraviolet ray (light) is used. Here,in the process portion 3, in order to fix the ink to the sheet S bycuring the ink, UV irradiators 61 and 62 (light irradiating portion) areprovided. In addition, the ink curing is performed by dividing theprocess into two steps including temporary curing and main curing.Between each of the plurality of recording heads 51, the UV irradiator61 for the temporary curing is disposed. In other words, by irradiatingthe ultraviolet ray having a small accumulated amount of light, the UVirradiator 61 cures (temporarily cures) the ink to the extent that theshape of the ink does not collapse, and does not completely cure theink. Meanwhile, on the downstream side in the transport direction Dswith respect to the plurality of recording heads 51, the UV irradiator62 for the main curing is provided. In other words, by irradiating theultraviolet ray having a large accumulated amount of light by the UVirradiator 61, the UV irradiator 62 completely cures (mainly cures) theink.

In this manner, the UV irradiator 61 disposed between each of theplurality of recording heads 51 temporarily cures the color inkdischarged to the sheet S from the recording head 51 that is on theupstream side in the transport direction Ds. Therefore, the inkdischarged to the sheet S by one recording head 51 is temporarily cureduntil reaching the recording head 51 adjacent to the one recording head51 that is on the downstream side in the transport direction Ds.Accordingly, generation of mixed color which is mixing of ink havingdifferent colors is suppressed. In a state where the mixed color issuppressed in this manner, the plurality of recording heads 51 dischargedifferent colors of ink, and form a color image on the sheet S.Furthermore, further on the downstream side in the transport directionDs than the plurality of recording heads 51, the UV irradiator 62 forthe main curing is provided. Therefore, the color image formed by theplurality of recording heads 51 is mainly cured by the UV irradiator 62,and is fixed to the sheet S.

Furthermore, on the downstream side in the transport direction Ds withrespect to the UV irradiator 62, the recording head 52 is also provided.The recording head 52 opposes the front surface of the sheet S woundaround the rotation drum 30 at a slight clearance, and dischargestransparent UV ink from the nozzle to the front surface of the sheet Sin the ink jet method. In other words, the transparent ink is furtherdischarged to the color image formed by the recording heads 51 for fourcolors. The transparent ink is discharged to the entire surface of thecolor image, and imparts texture, such as glossy sense or matt sense, tothe color image. In addition, on the downstream side in the transportdirection Ds with respect to the recording head 52, the UV irradiator 63is provided. As a strong ultraviolet ray is irradiated, the UVirradiator 63 completely cures (mainly cures) the transparent inkdischarged by the recording head 52. According to this, it is possibleto fix the transparent ink to the front surface of the sheet S.

However, in the printer 1 which records an image on the sheet S bydischarging the ink from the recording heads 51 and 52 in this manner,when an electrification amount of the sheet S is large, there is atendency for a large amount of mist-like ink to be fixed to the surfacewhich opposes the sheet S in the recording heads 51 and 52. As describedabove, since the first destaticizing portion 81 is provided in thedelivery portion 2, electrification of the sheet S is suppressed to acertain extent. However, in the process portion 3, in order to morereliably suppress adhesion of mist-like ink to the recording heads 51and 52, a second destaticizing portion 85 is provided. The seconddestaticizing portion 85 includes a front surface ionizer 86 whichopposes the front surface of the sheet S further on the upstream sidethan the uppermost recording head 51 in the transport direction Ds (thatis, between the driven roller 33 and the uppermost recording head 51 inthe transport direction Ds). In addition, the sheet S is destaticized bythe front surface ionizer 86. Furthermore, in the process portion 3, inorder to efficiently confirm destaticization of the sheet S, a potentialsensor S30 which detects a potential of the front surface of the sheet Sis provided. The rotation drum 30 detects the potential of the frontsurface of the sheet S wound around the rotation drum 30 between thesecond destaticizing portion 85 and the uppermost recording head 51 inthe transport direction Ds.

In this manner, in the process portion 3, the discharge and the curingof the ink are appropriately performed with respect to the sheet S woundaround the outer circumferential portion of the rotation drum 30, andthe color image coated with the transparent ink is formed. At this time,the sheet S which receives the printing of the color image in theprocess portion 3 receives the surface modification treatment in advancebefore reaching parts that oppose the recording heads 51 and 52. Sincethe color image is formed by discharging the ink to the sheet S to whichthe surface modification treatment is performed in this manner, it ispossible to form a color image having a high quality. In addition, thesheet S is destaticized before reaching parts that oppose the recordingheads 51 and 52. Therefore, it is possible to form the color image onthe sheet S while suppressing the fixing of a large amount of mist-likeink to the recording heads 51 and 52 since an electrification amount ofthe sheet S is large. In addition, the sheet S on which the color imageis formed is transported to the winding portion 4 by the outfeed roller32.

In addition to the winding shaft 40 around which the end of the sheet Sis wound, the winding portion 4 includes a driven roller 41 which windsthe sheet S from the rear surface side between the winding shaft 40 andthe outfeed roller 32. In a state where the front surface of the sheet Sis oriented to the outside, the winding shaft 40 winds and supports theend of the sheet S. In other words, when the winding shaft 40 rotates ina clockwise direction of FIG. 1, the sheet S transported from theoutfeed roller 32 is wound around the winding shaft 40 via the drivenroller 41. Incidentally, the sheet S is wound around the winding shaft40 via a core tube 42 which is attachable to and detachable from thewinding shaft 40. Therefore, when the sheet S wound around the windingshaft 40 is full, it is possible to detach the sheet S from each coretube 42.

However, as described above, the printer 1 includes the firstdestaticizing portion 81 disposed in the delivery portion 2, and thesecond destaticizing portion 85 disposed in the process portion 3. Next,a configuration of the first and second destaticizing portions 81 and 85will be described. FIG. 2 is a view schematically illustrating aconfiguration of the first destaticizing portion, and FIG. 3 is a viewschematically illustrating a configuration of the second destaticizingportion. In addition, the sheet S is also written in addition to thefirst destaticizing portion 81 in FIG. 2, and the sheet S and therotation drum 30 are also written in addition to the seconddestaticizing portion 85 in FIG. 3. In addition, a width direction Dwillustrated in both drawings is a direction which is orthogonal to thetransport direction Ds and is parallel to the front surface of therotation drum 30, that is, is a direction which is parallel to arotation shaft of the rotation drum 30.

As illustrated in FIG. 2, the first destaticizing portion 81 includesthe front surface ionizer 82 disposed on the front surface side of thesheet S, and the rear surface ionizer 83 disposed on the rear surfaceside of the sheet S. In the front surface ionizer 82, a plurality ofdischarge needles 821 which oppose the front surface of the sheet S atan interval d82 are arranged in a row at an equivalent pitch P82 to beparallel to the width direction Dw. In addition, in the rear surfaceionizer 83, a plurality of discharge needles 831 which oppose the rearsurface of the sheet S at an interval d83 are aligned in a row at anequivalent pitch P83 to be parallel to the width direction Dw. Here, theinterval d82 and the interval d83 are equivalent to each other, and thepitch P82 and the pitch P83 are equivalent to each other. In addition,the front surface ionizer 82 and the rear surface ionizer 83 arealternately positioned such that one discharge needle 821 and onedischarge needle 831 oppose each other nipping the sheet S. In addition,the front surface ionizer 82 and the rear surface ionizer 83 arepositioned with respect to the transport path Pc of the sheet S suchthat the row of the plurality of discharge needles 821 and the row ofthe plurality of discharge needles 831 protrude further to both sides inthe width direction Dw than the sheet S.

As illustrated in FIG. 3, the second destaticizing portion 85 includesthe front surface ionizer 86 disposed on the front surface side of thesheet S. In the front surface ionizer 86, the plurality of dischargeneedles 861 which oppose the front surface of the sheet S at an intervald86 are aligned in a row at an equivalent pitch P86 to be parallel tothe width direction Dw. Here, the interval d86 is wider than theinterval d82 and the interval d83 (d86>d82=d83), and the pitch P86 isgreater than the pitch P82 and the pitch P83 (P86>P82=P83). The frontsurface ionizer 86 is positioned with respect to the transport path Pcof the sheet S such that the row of the plurality of discharge needles861 protrudes further to both sides in the width direction Dw than thesheet S. In addition, the rotation drum 30 is positioned to protrudefurther to both sides in the width direction Dw than the row of theplurality of discharge needles 861 and the sheet S. Incidentally, theentire region of the front surface (circumferential surface) of therotation drum 30 is covered with a black insulating layer formed byalumite treatment. Therefore, parts on both sides of the sheet S whichprotrude to the discharge needle 861 are covered with the insulatinglayer without being covered by the sheet S on the front surface of therotation drum 30.

The description above is an outline of the apparatus configuration ofthe printer 1. Next, an electric configuration which controls theprinter 1 will be described. FIG. 4 is a block diagram illustrating theelectric configuration which controls the printer illustrated in FIG. 1.The printer 1 includes a printer control portion 100 which integrallycontrols each portion of the apparatus. The printer control portion 100is a computer configured of a central processing unit (CPU) or a memory.

In addition, the printer 1 includes a user interface (UI) 9. The UI 9includes a monitor configured of a liquid crystal display or the like,and an input operation portion configured of a keyboard or a mouse. Inaddition, on the monitor of the UI 9, a menu screen is displayed inaddition to the image of a printing target. Therefore, the user can opena printing setting screen from the menu screen, and set various printingconditions, such as a type of a printing medium, the size of theprinting medium, and printing quality, by operating the input operationportion of the UI 9 while confirming the monitor of the UI 9. Inaddition, a specific configuration of the UI 9 can be modified in avarious manners, and for example, the input operation portion may beconfigured of a touch panel of the monitor by using a touch panel typedisplay as a monitor. In addition, the printer control portion 100controls each portion of the apparatus of the recording head, the UVirradiator, and a sheet transport system as follows in accordance with acommand from an external apparatus or an input operation of the UI 9.

The printer control portion 100 controls an ink discharge timing of eachof the recording heads 51 which form the color image in accordance withthe transport of the sheet S. Specifically, the control of the inkdischarge timing is performed based on an output (detected value) of adrum encoder E30 which is attached to the rotation shaft of the rotationdrum 30 and detects a rotation position of the rotation drum 30. Inother words, in order to allow the rotation drum 30 to rotate to bedriven according to the transport of the sheet S, it is possible tograsp a transport position of the sheet S with reference to the outputof the drum encoder E30 that detects the rotation position of therotation drum 30. Here, as the printer control portion 100 generates aprint timing signal (pts) signal from the output of the drum encoderE30, and controls the ink discharge timing of each of the recordingheads 51 based on the pts signal, the ink discharged by each of therecording heads 51 lands at a target position of the transported sheetS, and the color image is formed.

In addition, the timing at which the recording head 52 discharges thetransparent ink is also similarly controlled by the printer controlportion 100 based on the output of the drum encoder E30. According tothis, it is possible to accurately discharge the transparent ink to thecolor image formed by the plurality of the recording heads 51.Furthermore, a timing of turning on and off or the irradiation amount ofthe UV irradiators 61, 62, and 63, is also controlled by the printercontrol portion 100.

In addition, the printer control portion 100 administers a function ofcontrolling the transport of the sheet S described in detail by usingFIG. 1. In other words, motors are connected to each of the deliveryshaft 20, the infeed roller 31, the outfeed roller 32, and the windingshaft 40, among the members which configure the sheet transport system.In addition, the printer control portion 100 controls a speed or torqueof each motor and controls the transport of the sheet S while rotatingthe motors. The transport control of the sheet S will be described indetail as follows.

The printer control portion 100 rotates a delivery motor M20 whichdrives the delivery shaft 20, and supplies the sheet S to the infeedroller 31 from the delivery shaft 20. At this time, the printer controlportion 100 controls torque of the delivery motor M20, and adjuststension (delivery tension Ta) of the sheet S to the infeed roller 31from the delivery shaft 20. In other words, a tension sensor S21 whichdetects the delivery tension Ta is attached to the driven roller 21disposed between the delivery shaft 20 and the infeed roller 31. Thetension sensor S21 can be configured of, for example, a load cell whichdetects a force received from the sheet S. In addition, the printercontrol portion 100 feedback-controls the torque of the delivery motorM20, and adjusts the delivery tension Ta of the sheet S based on thedetection result of the tension sensor S21.

In addition, the printer control portion 100 rotates a forward drivingmotor M31 which drives the infeed roller 31, and a rearward drivingmotor M32 which drives the outfeed roller 32. Accordingly, the sheet Sdelivered from the delivery portion 2 passes through the process portion3. At this time, while a speed control is performed with respect to theforward driving motor M31, a torque control is performed with respect tothe rearward driving motor M32. In other words, the printer controlportion 100 adjusts the rotation speed of the forward driving motor M31based on the output of the encoder of the forward driving motor M31.According to this, the sheet S is transported at a constant speed by theinfeed roller 31.

Meanwhile, the printer control portion 100 controls the torque of therearward driving motor M32, and adjusts tension (process tension Tb) ofthe sheet S from the infeed roller 31 to the outfeed roller 32. In otherwords, a tension sensor S34 which detects the process tension Tb isattached to a driven roller 34 disposed between the rotation drum 30 andthe outfeed roller 32. The tension sensor S34 can be configured of, forexample, a load cell which detects a force received from the sheet S. Inaddition, the printer control portion 100 feedback-controls the torqueof the rearward driving motor M32, and adjusts the process tension Tb ofthe sheet S based on the detection result of the tension sensor S34.

In addition, the printer control portion 100 rotates a winding motor M40which drives the winding shaft 40, and winds the sheet S transported bythe outfeed roller 32 around the winding shaft 40. At this time, theprinter control portion 100 controls torque of the winding motor M40,and adjusts the tension (winding tension Tc) of the sheet S to thewinding shaft 40 from the outfeed roller 32. In other words, a tensionsensor S41 which detects the winding tension Tc is attached to thedriven roller 41 disposed between the outfeed roller 32 and the windingshaft 40. The tension sensor S41 can be configured of, for example, aload cell which detects a force received from the sheet S. In addition,the printer control portion 100 feedback-controls the torque of thewinding motor M40, and adjusts the winding tension Tc of the sheet Sbased on the detection result of the tension sensor S41.

In addition, the printer control portion 100 administers a function ofcontrolling the corona treatment device 7. Specifically, the printercontrol portion 100 adjusts a voltage supplied to the corona dischargeelectrode 731 provided with the corona discharger 73. According to this,it is possible to adjust energy supplied for corona treatment, and tooptimize wettability of the ink with respect to the sheet S.

Furthermore, the printer control portion 100 optimizes destaticizingprocessing to the sheet S by controlling the first destaticizing portion81 and the second destaticizing portion 85. In particular, in the firstcontrol example of the destaticizing processing which will be describedlater, the printer control portion 100 controls the first destaticizingportion 81 and the second destaticizing portion 85 based on a result ofdetecting the front surface potential of the sheet S by the drum encoderE30.

FIG. 5 is a block diagram illustrating a configuration in which thefirst control example of destaticizing processing of the sheet isperformed. As illustrated in FIG. 5, the printer control portion 100includes a power source portion 110 which supplies a voltage to each ofthe discharge needles 821 included in the front surface ionizer 82 ofthe first destaticizing portion 81, a power source portion 120 whichsupplies a voltage to each of the discharge needles 831 included in therear surface ionizer 83 of the first destaticizing portion 81, and apower source portion 130 which supplies a voltage to each of thedischarge needles 861 included in the front surface ionizer 86 of thesecond destaticizing portion 85.

The power source portion 110 includes a DC power source 111, an AC powersource 112, and an amplifier 113 which adds an output of the AC powersource 112 to an output of the DC power source 111, and supplies anoutput voltage of the amplifier 113 to the discharge needle 821 of thefirst destaticizing portion 81. According to this, the output voltage ofthe DC power source 111 is imparted as a bias voltage, and an AC voltageoutput by the AC power source 112 is imparted focusing on the biasvoltage, with respect to the discharge needle 821. Accordingly, thedischarge needle 821 alternately and periodically emits positive ionsand negative ions in accordance with the supply of the AC voltage whichvibrates considering (focusing on) the bias voltage as a reference.

The power source portion 120 includes a DC power source 121, an AC powersource 122, and an amplifier 123 which adds an output of the AC powersource 122 to an output of the DC power source 121, and supplies anoutput voltage of the amplifier 123 to the discharge needle 831 of thefirst destaticizing portion 81. According to this, the output voltage ofthe DC power source 121 is imparted as a bias voltage, and an AC voltageoutput by the AC power source 122 is imparted focusing on the biasvoltage, with respect to the discharge needle 831. Accordingly, thedischarge needle 831 alternately and periodically emits positive ionsand negative ions in accordance with the supply of the AC voltage whichvibrates considering (focusing on) the bias voltage as a reference.

At this time, the discharge needle 821 and the discharge needle 831 arebiased to the same DC voltage to be equivalent to the DC voltage outputby the DC power source 111 and the DC voltage output by the DC powersource 121. In addition, the AC voltage output by the AC power source112 and the AC voltage output by the AC power source 122 have amplitudesand frequencies which are equivalent to each other. However, a phase ofthe AC voltage output by the AC power source 112 is different from aphase of the AC voltage output by the AC power source 122 by 180degrees. According to this, voltages reverse to each other are suppliedto each of the discharge needle 821 and the discharge needle 831focusing on the bias voltage. As a result, it is possible to efficientlysupply ions emitted from each of the discharge needles 821 and 831 ofthe first destaticizing portion 81 to the sheet S.

The power source portion 130 includes a DC power source 131, an AC powersource 132, and an amplifier 133 which adds an output of the AC powersource 132 to an output of the DC power source 131, and supplies anoutput voltage of the amplifier 133 to the discharge needle 861 of thesecond destaticizing portion 85. According to this, the output voltageof the DC power source 131 is imparted as a bias voltage, and an ACvoltage output by the AC power source 132 is imparted focusing on thebias voltage, with respect to the discharge needle 861. Accordingly, thedischarge needle 861 alternately and periodically emits positive ionsand negative ions in accordance with the supply of the AC voltage whichvibrates considering (focusing on) the bias voltage as a reference. Inaddition, in the example, the amplitude of the AC voltage output by theAC power source 132 is set to be 1 times or greater and less than 2times the amplitude of the AC voltage output by the AC power source 112and the AC power source 122.

Furthermore, the printer control portion 100 includes a feedback circuit140, and the feedback circuit 140 feedback-controls the output voltageof the DC power sources 111 and 121 of each of the power source portions110 and 120 based on the detected value of the potential sensor S30,that is, the bias voltage of the discharge needles 821 and 831.Specifically, the output voltage of the DC power sources 111 and 121 isfeedback-controlled such that the voltage detected by the potentialsensor S30 becomes close to a ground potential. According to this, anion balance of the first destaticizing portion 81 is adjusted.

FIG. 6 is a view schematically illustrating a temporal change in voltagegenerated by the first destaticizing portion and second destaticizingportion on the sheet. In FIG. 6, a horizontal axis indicates time t, anda vertical axis indicates voltage V. In addition, a curve illustrated bya solid line indicates a change in voltage generated by the firstdestaticizing portion 81 on the sheet S, and a curve illustrated by abroken line indicates a change in voltage generated by the seconddestaticizing portion 85 on the sheet S. In addition, the former changein voltage may be acquired by measuring the change in voltage on thesheet S at a part nipped by the front surface ionizer 82 and the rearsurface ionizer 83, or may be calculated from the change in voltage oftip ends of each of the discharge needle 821 and the discharge needle831 from the intervals d82 and d83. In addition, the latter change involtage may be acquired by measuring the change in voltage on the sheetS at a part which opposes the front surface ionizer 86, or may becalculated from the change in voltage of the tip end of the dischargeneedle 861 and the interval d86. The AC power source 112 sets the ACpower source and the amplitude of the AC voltage output by the AC powersource 132 as described above, and as a result, as illustrated in thedrawing, the amplitude of the AC voltage generated on the sheet S by thefirst destaticizing portion 81 is greater than the amplitude of the ACvoltage generated on the sheet S by the second destaticizing portion 85.

As described above, in the embodiment, the sheet S is destaticized bythe first destaticizing portion 81 further on the upstream side in thetransport direction Ds than the infeed roller 31 which drives the sheetS in the transport direction Ds. Therefore, since the sheet S isdestaticized when passing through the infeed roller 31, sticking of thesheet S to the infeed roller 31 is suppressed. As a result, it ispossible to accurately detect the process tension Tb of the sheet S inthe process portion 3 further on the downstream side in the transportdirection Ds than the infeed roller 31, and to appropriately perform thecontrol of the process tension Tb of the sheet S. In particular, theprocess tension Tb of the sheet S from the infeed roller 31 to theoutfeed roller 32 is tension of the sheet S which receives the dischargeof the ink from the recording heads 51 and 52 on the circumferentialsurface of the rotation drum 30. Therefore, from the viewpoint ofexcellent image recording, the process tension Tb becomes more importantthan other tensions Ta and Tc. Therefore, the embodiment which canappropriately perform the control of the process tension Tb is extremelyappropriate.

In addition, the corona treatment device 7 which performs surfacemodification treatment is provided on the sheet S by imparting dischargeenergy to the sheet S further on the upstream side in the transportdirection Ds than the first destaticizing portion 81. In the printer 1provided in the corona treatment device 7, since there is a tendency foran electrification amount of the sheet S to increase, influence on thetension control due to the sticking of the electrified sheet S to theinfeed roller 31 also increases. Meanwhile, by destaticizing the sheet Sby the first destaticizing portion 81 further on the upstream side inthe transport direction Ds than the infeed roller 31, it is possible toappropriately perform the tension control of the sheet S.

In addition, the second destaticizing portion 85 which destaticizes thesheet S is provided between the infeed roller 31 and the uppermostrecording head 51 in the transport direction Ds. In this manner, bydestaticizing the sheet S in two steps until reaching the recording head51, it is possible to suppress adhesion of mist-like ink to therecording head 51 due to the destaticization of the sheet S bydefinitely destaticizing the sheet S.

However, the second destaticizing portion 85 is provided to oppose therotation drum 30. According to this, it is possible to destaticize thesheet S in the vicinity of the recording head 51, and to efficientlysuppress adhesion of mist-like ink to the recording head 51 due to thedestaticization of the sheet S.

In addition, in the above-described embodiment, the front surface of therotation drum 30 is covered with the insulating layer. The reasonthereof is as follows. In other words, in a case where the front surfaceof the rotation drum 30 has conductivity, there is a concern that ionsgenerated by the second destaticizing portion 85 are oriented toward apart which is not hidden on the sheet S on the front surface of therotation drum 30, and the ions cannot be definitely imparted to thesheet S. Meanwhile, in the embodiment, by covering the front surface ofthe rotation drum 30 with the insulating layer, it is possible todefinitely impart the ions generated by the second destaticizing portion85 to the sheet S, and to more reliably destaticize the sheet S.

However, above, the first destaticizing portion 81 disposed on theupstream side and the second destaticizing portion 85 disposed on thedownstream side are provided in the transport direction Ds of the sheetS. In addition, the AC voltage having a relatively large amplitude isgenerated on the sheet S due to the AC voltage applied to the dischargeneedles 821 and 831 of the first destaticizing portion 81. Therefore,there is a tendency for ions to be concentrated and imparted to thesheet S at a part at which the discharge needles 821 and 831 oppose eachother. As a result, a large difference in applying amount of ionsbetween a part at which the ions are tightly imparted and a part atwhich the ions are sparsely imparted is generated, and unevendestaticization is likely to be generated on the sheet S destaticized bythe first destaticizing portion 81. Meanwhile, in the embodiment, thesecond destaticizing portion 85 further destaticizes the sheet S afterthe destaticization by the first destaticizing portion 81. However, asillustrated in FIG. 6, the amplitude of the AC voltage generated on thesheet S by the AC voltage applied to the discharge needle 861 of thesecond destaticizing portion 85 is smaller than the amplitude of the ACvoltage generated on the sheet S by the AC voltage applied to thedischarge needles 821 and 831 of the first destaticizing portion 81.Therefore, the second destaticizing portion 85 can similarly destaticizethe sheet S compared to the first destaticizing portion 81, and it ispossible to mitigate uneven destaticization of the sheet S after thedestaticization by the first destaticizing portion 81. As a result, itis possible to suppress adhesion of mist-like liquid to the recordinghead 51.

At this time, the first destaticizing portion 81 includes the pluralityof discharge needles 821 provided on the front surface side of the sheetS, and the plurality of discharge needles 831 provided on the rearsurface side of the sheet S, and the phase of the AC voltage applied tothe plurality of discharge needles 821 on the front surface side isdifferent from the phase of the AC voltage applied to the plurality ofdischarge needles 831 on the rear surface side by 180 degrees. In theconfiguration, the AC voltage having a relatively large amplitude isgenerated on the sheet S by the AC voltage applied to the dischargeneedles 821 and 831 of the first destaticizing portion 81. Here, it isappropriate to mitigate uneven destaticization of the sheet S after thedestaticization by the first destaticizing portion 81 by providing thesecond destaticizing portion 85 as described above.

In addition, the intervals d82 and d83 between the discharge needles 821and 831 of the first destaticizing portion 81 and the sheet S arenarrower than the interval d86 between the discharge needle 861 of thesecond destaticizing portion 85 and the sheet S. In the configuration,the AC voltage having a relatively large amplitude is generated on thesheet S by the AC voltage applied to the discharge needles 821 and 831of the first destaticizing portion 81. Here, as described above, it isappropriate to mitigate uneven destaticization of the sheet S after thedestaticization by the first destaticizing portion 81 by providing thesecond destaticizing portion 85.

In addition, the pitches P82 and P83 at which the plurality of dischargeneedles 821 and 831 are arranged in the first destaticizing portion 81are different from the pitch P86 at which the plurality of dischargeneedles 861 are arranged in the second destaticizing portion 85. In thismanner, by making the pitches P82, P83, and P86 at which the dischargeneedles 821, 831, and 861 are arranged different in the firstdestaticizing portion 81 and in the second destaticizing portion 85, itis possible to more efficiently mitigate uneven destaticization of thesheet S after the destaticization by the first destaticizing portion 81by the second destaticizing portion 85.

In addition, the DC power sources 111 and 121 which adjust the ionbalance of the first destaticizing portion 81, and the potential sensorS30 which detects the potential of the sheet S supported by the rotationdrum 30 are provided. In the configuration, it is possible to adjust theion balance of the first destaticizing portion 81 while confirming thedetection result of the potential of the sheet S supported by therotation drum 30. Therefore, it is possible to optimize the ion balance.As a result, it is possible to suppress the adhesion of mist-like liquidto the recording head 51.

In particular, the feedback circuit 140 which controls the ion balanceof the first destaticizing portion 81 is provided by adjusting the ionbalance of the first destaticizing portion 81 to the DC power sources111 and 121 based on the detection result of the potential sensor S30.In the configuration, it is possible to automatically optimize the ionbalance by the feedback circuit 140.

As described above, in the above-described embodiment, the printer 1corresponds to an example of “printing apparatus” of the invention, theinfeed roller 31 corresponds to an example of “driving roller” of theinvention, the rotation drum 30 corresponds to an example of “supportingmember” of the invention, the recording heads 51 and 52 correspond to anexample of “discharge head” of the invention, the printer controlportion 100, the tension sensor S34, the outfeed roller 32, and therearward driving motor M32 cooperate with each other and function as anexample of “tension control portion” of the invention, the firstdestaticizing portion 81 corresponds to an example of “firstdestaticizing portion” of the invention, the sheet S corresponds to anexample of “recording medium” of the invention, the transport directionDs corresponds to an example of “predetermined direction” of theinvention, and the process tension Tb corresponds to an example of“tension” of the invention. In addition, the corona treatment device 7corresponds an example of “discharger” of the invention, the seconddestaticizing portion 85 corresponds to an example of “seconddestaticizing portion” of the invention, the discharge needle 821 andthe discharge needle 831 correspond to an example of “electrode” of“first destaticizing portion” of the invention, the discharge needle 861corresponds to an example of “electrode” of “second destaticizingportion” of the invention, the interval d82 and the interval d83correspond to an example of “interval between the electrode of the firstdestaticizing portion and the recording medium” of the invention, theinterval d86 corresponds to an example of “interval between theelectrode of the second destaticizing portion and the recording medium”of the invention, the pitch P82 and the pitch P83 correspond to anexample of “pitch at which the plurality of electrodes are arranged inthe first destaticizing portion” of the invention, the pitch P86corresponds to an example of “pitch at which the plurality of electrodesare arranged in the second destaticizing portion” of the invention, theDC power source 111 and the DC power source 121 correspond to an exampleof “adjustment portion” of the invention, the potential sensor S30corresponds to an example of “potential detection portion” of theinvention, and the feedback circuit 140 corresponds to an example of“balance control portion” of the invention.

In addition, the invention is not limited to the above-describedembodiment, and it is possible to add various changes to theabove-described embodiments as long as the changes do not depart fromthe idea. Therefore, a configuration illustrated in FIG. 7 is alsopossible. Here, FIG. 7 is a block diagram illustrating a configurationin which a second control example of the destaticizing processing of thesheet is performed. Here, a difference from the configurationillustrated in FIG. 5 is mainly described, and common configurationelements are given the same reference numerals and the descriptionthereof will be omitted. However, it is needless to say that similareffects are achieved by providing the configuration common to thosedescribed above.

In the second control example illustrated in FIG. 7, the printer controlportion 100 includes a display control circuit 150, and the displaycontrol circuit 150 displays the potential detected by the potentialsensor S30 on a display 91 of the UI 9. Therefore, the user can confirmthe potential of the sheet S on the rotation drum 30 by the display 91.In addition, in the UI 9, a volume knob 92 which adjusts an outputpotential of the DC power source 111, and a volume knob 93 which adjustsan output potential of the DC power source 121, are provided. Therefore,it is possible to adjust the bias voltage supplied to the dischargeneedles 821 and 831 by operating the volume knobs 92 and 93 whileconfirming the potential of the sheet S on the rotation drum 30 by thedisplay 91.

In this manner, the display 91 (display portion) which displays thedetection result of the potential sensor S30, and the volume knobs 92and 93 (balance control portion) which adjust the ion balance of thefirst destaticizing portion 81 to the DC power sources 111 and 121 inaccordance with the input operation, are provided. According to this,the user can optimize the ion balance by performing the input operationto the volume knobs 92 and 93 while confirming the detection result ofthe potential sensor S30 displayed on the display 91.

In addition, a specific configuration of the first destaticizing portion81 may be appropriately changed. For example, the first destaticizingportion 81 may be placed on a conductive (metal) flat plate grounded toone of the front surface ionizer 82 or the rear surface ionizer 83, ormay be removed. In addition, the first destaticizing portion 81 can alsobe configured of one ionizer by omitting one of the front surfaceionizer 82 or the rear surface ionizer 83. It is also possible toappropriately change the pitches P82 and P83 of the discharge needles821 and 831 or the intervals d82 and d83 between the discharge needles821 and 831 and the sheet S. Furthermore, the disposition of the firstdestaticizing portion 81 may be changed, and for example, the firstdestaticizing portion 81 may be disposed between the supporting roller71 and the driven roller 21, or further on the downstream side in thetransport direction Ds than the infeed roller 31.

In addition, a specific configuration of the second destaticizingportion 85 may be appropriately changed. Therefore, it is also possibleto appropriately change the pitch P86 of the discharge needle 861 of thefront surface ionizer 86 or the interval d86 between the dischargeneedle 861 and the sheet S. In addition, the disposition of the seconddestaticizing portion 85 may be changed, or the second destaticizingportion 85 may be omitted.

In addition, in the example of FIG. 5, the feedback control isintegrally performed with respect to the DC power sources 111 and 121.However, the feedback control may be performed separately with respectto the DC power sources 111 and 121. In addition, in the example of FIG.7, a configuration of adjusting the output potential of the DC powersources 111 and 121 separately is illustrated. However, the outputpotential of the DC power sources 111 and 121 may be configured to beintegrally adjusted. Furthermore, a configuration in which the potentialsensor S30 is provided, or a configuration in which the output potentialof the DC power sources 111 and 121 is variable, is also not necessary.

In addition, in the above-described embodiment, the sheet S is supportedby the cylindrical rotation drum 30. However, the shape of the memberwhich supports the sheet S is not limited thereto, and for example, thesheet S may be supported on the front surface of a flat plate.

This application claims priority under 35 U.S.C. §119 to Japanese PatentApplication No. 2016-087210, filed Apr. 25, 2016. The entire disclosureof Japanese Patent Application No. 2016-087210 is hereby incorporatedherein by reference.

What is claimed is:
 1. A printing apparatus comprising: a driving rollerwhich drives a recording medium in a predetermined direction by rotationthereof; a supporting member which supports the recording medium furtheron the downstream side in the predetermined direction than the drivingroller; a discharge head which is provided to oppose the supportingmember and discharges liquid to the recording medium supported by thesupporting member; a tension control portion which adjusts tension ofthe recording medium supported by the supporting member by controllingtension of the recording medium based on a result of detecting tensionof the recording medium further on the downstream side in thepredetermined direction than the driving roller; and a firstdestaticizing portion which destaticizes the recording medium further onthe upstream side in the predetermined direction than the drivingroller.
 2. The printing apparatus according to claim 1, furthercomprising: a discharger which performs surface modification treatmentwith respect to the recording medium by imparting discharge energy tothe recording medium further on the upstream side in the predetermineddirection than the first destaticizing portion.
 3. The printingapparatus according to claim 1, further comprising: a seconddestaticizing portion which destaticizes the recording medium betweenthe driving roller and the discharge head.
 4. The printing apparatusaccording to claim 3, wherein the second destaticizing portion isprovided to oppose the supporting member.
 5. The printing apparatusaccording to claim 4, wherein a front surface of the supporting memberis covered with an insulating layer.
 6. The printing apparatus accordingto claim 4, wherein the first destaticizing portion and the seconddestaticizing portion destaticize the recording medium by imparting ionsgenerated by applying an AC voltage to a plurality of arrangedelectrodes to the recording medium, and wherein an amplitude of an ACvoltage generated in the recording medium by the AC voltage applied tothe electrode of the second destaticizing portion is smaller than anamplitude of an AC voltage generated in the recording medium by the ACvoltage applied to the electrode of the first destaticizing portion. 7.The printing apparatus according to claim 6, wherein the firstdestaticizing portion has a plurality of electrodes provided on onesurface side of the recording medium and a plurality of electrodesprovided on the other surface side of the recording medium, and whereina phase of the AC voltage applied to the plurality of electrodes on theone surface side and a phase of the AC voltage applied to the pluralityof electrodes on the other surface side are different from each other by180 degrees.
 8. The printing apparatus according to claim 6, wherein aninterval between the electrode of the first destaticizing portion andthe recording medium is narrower than an interval between the electrodeof the second destaticizing portion and the recording medium.
 9. Theprinting apparatus according to claim 6, wherein a pitch at which theplurality of electrodes are arranged in the first destaticizing portionis different from a pitch at which the plurality of electrodes arearranged in the second destaticizing portion.
 10. The printing apparatusaccording to claim 1, further comprising: an adjustment portion whichadjusts an ion balance of the first destaticizing portion; and apotential detector which detects a potential of the recording mediumsupported by the supporting member.
 11. The printing apparatus accordingto claim 10, further comprising: a balance control portion whichcontrols an ion balance of the first destaticizing portion by adjustingthe ion balance of the first destaticizing portion to the adjustmentportion based on the detection result of the potential detector.
 12. Theprinting apparatus according to claim 10, further comprising: a displayportion which displays the detection result of the potential detector;and a balance control portion which adjusts an ion balance of the firstdestaticizing portion to the adjustment portion in accordance with aninput operation.
 13. A printing method comprising: driving a recordingmedium in a predetermined direction by a driving roller by rotating thedriving roller; destaticizing the recording medium by a destaticizingportion further on the upstream side in the predetermined direction thanthe driving roller; adjusting tension of the recording medium supportedby the supporting member by controlling tension of the recording mediumbased on a result of detecting tension of the recording medium furtheron the downstream side in the predetermined direction than the drivingroller; and discharging liquid from a discharge head that opposes thesupporting member, to the recording medium supported by the supportingmember provided further on the downstream side in the predetermineddirection than the driving roller.